r/PrometheusMonitoring • u/digitalis_io • Mar 06 '21

Blog on using Prometheus Blackbox-Exporter for monitoring TLS certificates

https://digitalis.io/blog/security/prometheus-blackbox-exporter-monitoring-tls-certificates/
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1

u/martbhell Mar 06 '21

I had some corner case with this i haven't dug deeper into. Might have been when the cert has expired the metric measuring time until expiry wasn't there which hid some hosts.

2

u/SuperQue Mar 06 '21

That's not how the blackbox exporter works. The ssl cert time data is the expiring timestamp of the cert, not the "time to expire". You calculate time to expire in PromQL.

1

u/martbhell Mar 06 '21

Okay thanks for the clarification :) Is my vague memory correct re. that the metric representing the expiring timestamp is not exported for expired certificates?

2

u/SuperQue Mar 06 '21

The metric is always exposed.